1. Field
The invention is in the field of fire or other emergency doors which are generally maintained open during normal situations, but in case of fire and sometimes other emergencies, are closed, often automatically.
2. State of the Art
Fire doors which serve to seal off an area of a building in the event of a fire are commonly required in public buildings. Increasingly, strict requirements for such doors are being imposed. In new installations it is not unusual that codes require that the doors, when dosed, provide a fire seal from one side to the other and maintain integrity and the seal for set periods of time with extreme fire temperature on one side of the door. This requires that any cracks between a door and the door frame and between doors themselves when double doors are used be effectively sealed against heat and fire transfer. Further, in many cases, these doors are normally maintained in open condition and are automatically closed by a mechanical door closer apparatus when an emergency condition is detected. Thus, the doors must close easily.
U.S. Pat. No. 3,973,289 shows a door hinge which includes a curved hinge piece extending between a door jamb mounting channel and a door mounting channel wherein the hinge piece rotates in the respective mounting channels to allow swinging of the door. This arrangement provides hinging of the door along the entire hinged side of the door, and seals any gaps that otherwise would be present between the door and door jamb with traditional hinges. In order to prevent relative longitudinal (vertical) movement of the door with respect to the hinge piece and of the hinge piece with respect to the jamb mounting, it is necessary to install and maintain hanger straps which stretch between the top of the hinge piece to the bottom of the door and from the top of the jamb channel to the bottom of the hinge piece.
U.S. Pat. Nos. 3,969,845, 4,093,284, and 4,545,607 show doors including a nose piece extending along the forward edge of the door and rotatably or pivotally mounted thereto so that in closing the door, the nose piece rotates into a closed position about a mating projection on the door frame or adjacent door to close any gap along the forward edge of the door that might otherwise be present when the door is closed and to lock the door in closed position. In such doors, the rotating nose piece of the door is rotated into its dosed position by the force on the door and the nose piece as the door is closed. Thus, the door must be closed with enough force to rotate the nose piece. The nose piece is locked into its rotated, closed position when the door is closed to maintain and lock the door in such closed condition.
Numerous emergency or exit doors are known wherein the doors are held in closed position by latching elements which extend from the door, usually from the top edge, the bottom edge, or both, into receiving recesses. Hardware for operating such doors usually takes the form of so called "panic hardware" wherein a push bar is provided on one side of the door which is pushed to retract the latching elements and open the door. Generally, all of the hardware and the latching elements operated thereby are hung on the outside of the door. Thus, the hardware extends from the side of the door and is completely visible.